Groundwater contamination by a host of water soluble organic and inorganic compounds such as gasoline, polychlorobiphenyls, arsenic, chromium, and nickel present a serious threat to health and human safety. Investigation and remediation are now required by most state and local governments. Integral to the investigation and remediation of groundwater contamination is the sampling of said groundwater to both identify and quantify the pollutants present. There are currently four major methods of obtaining groundwater samples; the open-top bailer, the double-ended COLAWASA sampler, the evacuated-vial sampler, the pressure-pumping sampler, and the Fletcher Sampler. These methods all have the same failings to varying degrees; their action of sample collection causes unusually high turbidity in the obtained water sample, they all require "transfer" of the sampled groundwater to a sample container of some type which results in sample concentration losses and sampling error, and their use requires well purging. The Fletcher sampler is not used for groundwater sampling, but rather for limnolgical and oceanographic sampling.
The open-top bailer is a simple device employing a vertical cylinder into the bottom of which a check-valve of some type is installed. The bailer has a blunt, non-hydrodynamic shape and causes a mixing of the groundwater column, usually resulting in loss of discrete sampling capability and high turbidity in the retrieved sample. The method of operation involves simply lowering the bailer down a groundwater monitoring well past the air-water interface, opening the check valve and allowing the bailer to fill. The bailer is then retrieved to the surface and the groundwater sample transferred by pouring into a sampling container for preservation and transport to a laboratory for identification and quantification. The action of transferring the sample to a sampling container causes splashing and volatilization of volatile organic components resulting in inaccurate quantification of field conditions. Decontamination of the sampling device is not difficult, but it is lengthy.
The double-ended COLAWASA sampler is a 2-meter-long plastic or glass tube, having rubber plugs at either end, attached through their centers with an elastic cord. The COLAWASA sampler has a blunt, non-hydrodynamic shape and causes a mixing of the groundwater column, usually resulting in loss of discrete sampling capability and high turbidity in the retrieved sample. The method of operation involves cocking the two plugs in the open position and simply lowering the COLAWASA sampler down a groundwater monitoring well past the air-water-interface, a tug on the lowering line triggers the plugs at either end to plug the open tube. The COLAWASA sampler is then retrieved to the surface and the groundwater sample transferred by pouring into a sampling container for preservation and transport to a laboratory for identification and quantification. The action of transferring the sample to a sampling container causes splashing and volatilization of volatile organic components resulting in inaccurate quantification of field conditions. Decontamination of the sampling device is difficult and complicated.
The evacuated vial sampler involves an elaborate system of flexible weights, piercing syringe needles, evacuated septum-equipped vials, and a vacuum pump. The sampler operates by evacuating a laboratory-cleaned, septum-equipped glass vial, installing the vial in a cage-like holder which is equipped with a syringe needle and flexible weight system. The entire system is then lowered into a groundwater monitoring well and allowed to hit the bottom of the well. The weights push the vial forward onto the syringe needle, piercing the septum and allowing groundwater to be drawn up into the vial, through the needle, by vacuum pressure. The evacuated vial sampler has a blunt, non-hydrodynamic shape and causes a mixing of the groundwater column, particularly at the bottom of the well, usually resulting in loss of discrete sampling capability and extremely high turbidity in the retrieved sample. The sample is retrieved in its original sampling container, but bubbles in the container usually result in loss of dissolved volatiles. Decontamination of the sampling device is difficult and complicated.
The pressure-pumping sampler involves a down-well pump of some particular operational type. The pressure-pumping sampler has a blunt, non-hydrodynamic shape and causes a mixing of the groundwater column, particularly at the bottom of the well, usually resulting in loss of discrete sampling capability and extremely high turbidity in the retrieved sample. The sample is pumped to the surface where it is captured in an open sampling container. The resultant introduction of finely diffused air during pumping, and the splashing-action of the retrieved groundwater as it is captured in the container guarantee loss of dissolved volatile organic compounds during the sample process. Decontamination of the sampling device is difficult and complicated.
The Fletcher Sampler involves a metal canister into which a 500 milliliter glass bottle sample container, fitted with a ground-glass fritted stopper (when closed), is placed for filling. This canister-type sampler is used primarily for sampling lake or sea water, particularly for chemical oxygen demand studies, but is also commonly used for sewage studies as well. The shape is generally cylindrical, usually 41/2- to 5-inches in diameter and 71/2- to 8-inches tall, having a flat bottom and a mostly flat top; the entire assembly is generally lowered by way of a thin chain or a nylon cord. The filling mechanism uses a flexible filling tube and a rigid exhaust tube. The flexible filling tube is connected to a rigid tube which pierces through the canister lid, entering the glass neck of the 500 milliliter sample bottle; the sample bottle rests on the bottom of the inside of the canister. The flexible sampling tube is usually strapped to the outside of the canister so as to sample the water closest to the bottom of the lake or sea-bed. As the sampler is lowered to the bottom of the lake or sea-bed, sampling begins, flushing the 500 milliliter sample bottle. This sampler is primarily used for obtaining samples for analysis of the chemical oxygen demand (COD) and biological oxygen demand (BOD) of the water being sampled, and is not generally used for collecting samples of groundwater from groundwater monitoring wells.